US 7,605,646 B2 · Low glitch offset correction circuit for auto-zero sensor amplifiers and method

Abstract

An instrumentation amplifier includes first (11A) and second (12A) input amplifiers having outputs (15A,B) coupled to an output amplifier (13). A first auto-zero stage (20) in the first input amplifier is auto-zeroed to a first voltage level (VREFL), a first input signal (Vin+) is amplified by a second auto-zero stage (24) in the first input amplifier, and the amplified first input signal is coupled to the output amplifier, during a first phase (A). A third auto-zero stage (44) in the second input amplifier is auto-zeroed to a second voltage level (VREFH), a second input signal (Vin−) is amplified by a fourth auto-zero stage (40) in the second input amplifier, and the amplified second input signal is coupled to the output amplifier, during a second phase (B). The second auto-zero stage is auto-zeroed to the first voltage level, the first input signal is amplified by the first auto-zero stage (20), and the amplified first input signal is coupled to the output amplifier, during a third phase (C). The fourth auto-zero stage is auto-zeroed to a the second voltage level, the second input signal is amplified by the third auto-zero stage, and the amplified second input signal is coupled to the output amplifier, during a fourth phase (D).

Claims20

Dependent claims

Instrumentation amplifier circuitry comprising:

first and second input amplifiers each having a first input, a second input, and an output, a chopped voltage reference circuit producing alternating first and second reference voltage levels on first and second terminals thereof;
first and second auto-zero stages, first, second, third and fourth input switches, and first, second, third and fourth output switches in the first input amplifier;
third and fourth auto-zero stages, fifth, sixth, seventh and eighth input switches, and fifth, sixth, seventh and eighth output switches in the second input amplifier;
and
a control circuit for generating various control signals to control the chopped voltage reference circuit, various input switches, and various output switches;
wherein the control circuit operates the various input switches and the various output switches during first, second, third and fourth phases so as to auto-zero the first auto-zero stage to the first voltage level during the first phase, auto-zero the third auto-zero stage to the second voltage level during the second phase, auto-zero the second auto-zero stage to the first voltage level during the third phase, and auto-zero the fourth auto-zero stage to the second voltage level during the fourth phase.

3 more elements

A method of operating instrumentation amplifier circuitry including a first input amplifier having a first input receiving a first input signal, a first output, and a second input receiving a first feedback signal from the gain circuit, and a second input amplifier having a first input receiving a second input signal, a second output, and a second input receiving a second feedback signal from the gain circuit, the method comprising:

repetitively producing alternating first and second reference voltage levels on first and second terminals of a reference circuit during successive phases, respectively;
auto-zeroing a first auto-zero stage in the first input amplifier to the first voltage level, amplifying the first input signal by means of a second auto-zero stage in the first input amplifier, and coupling the amplified first input signal to the first output, all during a first phase;
auto-zeroing a third auto-zero stage in the second input amplifier to the second voltage level, amplifying the second input signal by means of a fourth auto-zero stage in the second input amplifier, and coupling the amplified second input signal to the second output, all during a second phase which follows the first phase;
auto-zeroing the second auto-zero stage to the first voltage level, amplifying the first input signal by means of the first auto-zero stage, and coupling the amplified first input signal to the first output, all during a third phase which follows the second phase;
and
auto-zeroing the fourth auto-zero stage to a the second voltage level, amplifying the second input signal by means of the third auto-zero stage, and coupling the amplified second input signal to the second output, all during a fourth phase which follows the third phase.

3 more elements

Instrumentation amplifier circuitry comprising:

a first input amplifier having a first input receiving a first input signal, a first output, and a second input receiving a first feedback signal from the gain circuit, and a second input amplifier having a first input receiving a second input signal, a second output, and a second input receiving a second feedback signal;
means for repetitively producing alternating first and second reference voltage levels on first and second terminals of a reference circuit during successive phases, respectively;
means for auto-zeroing a first auto-zero stage in the first input amplifier to the first voltage level, amplifying the first input signal by means of a second auto-zero stage in the first input amplifier, and coupling the amplified first input signal to the first output, all during a first phase;
means for auto-zeroing a third auto-zero stage in the second input amplifier to the second voltage level, amplifying the second input signal by means of a fourth auto-zero stage, and coupling the amplified second input signal to the second output, all during a second phase which follows the first phase;
means for auto-zeroing the second auto-zero stage to the first voltage level, amplifying the first input signal by means of the first auto-zero stage, and coupling the amplified first input signal to the first output, all during a third phase which follows the second phase;
and
means for auto-zeroing the fourth auto-zero stage to a the second voltage level, amplifying the second input signal by means of the third auto-zero stage, and coupling the amplified second input signal to the second output, all during a fourth phase which follows the third phase.

4 more elements

Dependencies are inferred from the claim text.

Low glitch offset correction circuit for auto-zero sensor amplifiers and method

Life of this patent

Low glitch offset correction circuit for auto-zero sensor amplifiers and method

Life of this patent

Abstract

Claims20